This invention relates generally to electrophotographic printing, and more particularly, a cleaning blade used therein to remove particles adhering to the photoconductive member.
In the process of electrophotographic printing, a photoconductive surface is charged to a substantially uniform potential. The photoconductive surface is imagewise exposed to record an electrostatic latent image corresponding to the informational areas of an original document being reproduced. This records an electrostatic latent image on the photoconductive surface corresponding to the informational areas contained within the original document. Thereafter, a developer material is transported into contact with the electrostatic latent image. Toner particles are attracted from the carrier granules of the developer material onto the latent image. The resultant toner powder image is then transferred from the photoconductive surface to a sheet of support material and permanently affixed thereto.
This process is well known and useful for light lens copying from an original and printing applications from electronically generated or stored originals, and in ionography.
In a reproduction process of the type as described above, it is inevitable that some residual toner will remain on the imaging (i.e. photoreceptive, photoconductive) surface after the toner image has been transferred to the sheet of support material (e.g. paper). It has been found that with such a process that the forces holding some of the toner particles to the imaging surface are stronger than the transfer forces and, therefore, some of the particles remain on the surface after transfer of the toner image. In addition to the residual toner, other particles, such as paper debris (i.e. Kaolin, fibers, clay), additives and plastic, are left behind on the surface after image transfer. (Hereinafter, the term "residual particles" encompasses residual toner and other residual particles remaining after image transfer.) The residual particles adhere firmly to the surface and must be removed prior to the next printing cycle to avoid its interfering with recording a new latent image thereon.
Various methods and apparatus may be used for removing residual particles from the photoconductive imaging surface. Hereinbefore, a cleaning brush, a cleaning web, and a cleaning blade have been used. Both cleaning brushes and cleaning webs operate by wiping the surface so as to affect transfer of the residual particles from the imaging surface thereon. After prolonged usage, however, both of these types of cleaning devices become contaminated with toner and must be replaced. This requires discarding the dirty cleaning devices. In high-speed machines this practice has proven not only to be wasteful but also expensive.
The shortcomings of the brush and web made way for another now prevalent form of cleaning known and disclosed in the art--blade cleaning. Blade cleaning involves a blade, normally made of a rubberlike material (i.e. polyurethane) which is dragged or wiped across the surface to remove the residual particles from the surface. Blade cleaning is a highly desirable method, compared to other methods, for removing residual particles due to its simple, inexpensive structure. However, there are certain deficiencies in blade cleaning which are primarily a result of the frictional sealing contact that must occur between the blade and the surface. This frictional sealing contact often leads to blade failure and as a result requires blade replacement.
To change a cleaning blade in a conventional xerographic copier a customer service engineer (CSE), technical representative or the like, must, for every blade change, perform sometimes as many as a 24 step process that includes completely removing the photoreceptor belt module.
The present process for installing the cleaning blade (average size of the cleaning blade is about a 37 cm.times.1.8 cm.times.0.2 cm urethane slab) in its present holder requires the CSE to push the blade into the holder channel until the blade reaches maximum penetration (about 1.1 cm) along the entire length of the blade. This is not a simple operation. The blade uses a friction fit to hold the blade in position inside its holder. The blade's snug fit causes it to stick to the sides of the holder and resist being pressed into the channel. Since the blade is pliable, the blade bends as the CSE tries to push it into its proper position, making the job difficult.
It requires a lot of practice to be able to accomplish the task of installing a new blade in this manner. Even after the blade is finally inserted into the holder channel, it is not obvious whether or not the blade is properly aligned for an even cleaning edge. Although cleaning blades have been able to clean when installed slightly skewed, a skewed blade can also cause photoreceptor tracking problems. These tracking problems can cause premature failure of the photoreceptor and other failures. A skewed cleaning blade also wears unevenly and causes premature failure of the blade also. It is an object of the present invention to provide an easier means for inserting the blade so that skewing of the blade does not occur.
The following disclosures may be relevant to various aspects of the present invention and may be briefly summarized as follows:
U.S. Pat. No. 4,202,437 to Gordon discloses a conveyor belt scraper assembly to remove foreign matter from a conveyor belt. This design allows rapid and efficient replacement of worn out blades. The scraper assembly is mounted on a pair of slide housings which allows adjustment of the angular orientation of the blade to compensate for substantial wear on the scraper edge. A scraper core holds three blades, all 120 degrees apart which may be used substitutively when one blade wears out. The blades consist of two working edge surfaces so that when one surface is diminished and unusable, the mounting can be reversed to provide a new working surface.
U.S. Pat. No. 4,311,094 to Ellison discloses a method and apparatus for removing foreign matter from a printing plate mounted on a cylinder. A pair of parallel, spaced flexible blades contact the surface of the plate whereby one blade spreads and thins ink on a surface while the other blade dislodges and removes them from the surface. The blades are supported by a mounting member which extends across the entire width of the printing plate and is parallel to the axis of the plate cylinder.
U.S. Pat. No. 4,328,888 to Luke discloses a conveyor belt scraper blade in which one longitudinal axis makes contact with a conveyor belt surface to be scraped. The blade extends in opposite lateral directions beyond the periphery of a metallic reinforcing strip to provide two scraper edges. The hard rubber blade, bonded to a metallic reinforcing strip, makes contact with the conveyor belt and scrapes foreign matter therefrom. After wearing of one edge of the blade, the worn blade may be released from the supporting arrangement and reversed to present its' other edge to the belt surface.